LONDON — For the first time since the government of Hungary threatened to shutter the university he founded in Budapest, the American financier and philanthropist George Soros criticized the country’s right-wing prime minister, Viktor Orban, saying he has presided over a “mafia state.”

In a keynote speech Thursday at the annual economic forum of the European Commission, Mr. Soros cited “the deception and corruption of the mafia state the Orban regime has established” and praised those who protested a law passed in April that seemed designed to close the school, the Central European University.

Mr. Soros, a benefactor of civil society groups in his native Hungary and elsewhere, founded the C.E.U. in 1991 and endowed it to operate as an independent American institution in Hungary. The law passed by the Hungarian Parliament in April would effectively force the closing of the university because it does not operate a campus in the United States, where it is registered.

The law was widely viewed as a crackdown on free expression and liberal values under Mr. Orban, who has called the university a fraud and accused Mr. Soros of fomenting dissent against the government.

In his speech Thursday, Mr. Soros denied he was trying to interfere in Hungarian politics, and chastised Mr. Orban for trying to cast him as an enemy.

“He sought to frame his policies as a personal conflict between the two of us and has made me the target of his unrelenting propaganda campaign,” Mr. Soros said of the Hungarian prime minister. “He cast himself in the role of the defender of Hungarian sovereignty and me as a shady currency speculator who uses his money to flood Europe — particularly his native Hungary — with illegal immigrants as part of some vague but nefarious plot.”

Mr. Soros added, “This is the opposite of who I am.”

Opponents of the law have said it threatens not just C.E.U. but academic freedom in Hungary. Tens of thousands of people took to the streets of Budapest in April to protest the law. The European Commission took legal action and the European Parliament voted to begin a procedure that would penalize the Hungarian government for violating the bloc’s fundamental values.

The situation had been at a standstill for months until last week, when Andrew M. Cuomo, the governor of New York, where the university is registered, said in a statement that the state was open to negotiations. Hungary has said the same, and the government sent responses to the European Commission’s legal concerns in the case.

Mr. Orban’s chief of staff, Janos Lazar, said Thursday that accusations of a “mafia state” apply better to the nongovernment organizations that receive funding from Mr. Soros’s Open Society Foundations.

“These organizations, financed by George Soros, have operated like mafia,” Mr. Lazar said at a news briefing in Budapest on Thursday, repeating allegations of lack of transparency.

Defenders of human rights, refugees and those who promote the fight against corruption that sometimes get support from Mr. Soros have in recent years been the targets of government scrutiny. One such organization, the Hungary branch of Transparency International, which receives less than 10 percent of its funding from grants supported by Mr. Soros, lauded his comments Thursday.

“Open Society foundations is a very important partner, and we take Mr. Soros’s words as encouragement,” Miklos Ligeti, the group’s legal director, said in a phone interview from Budapest.

Mr. Soros, whose speech was focused more broadly on changes to the European Union, called on the bloc’s institutions to act against the challenges to democracy posed by Hungary and Poland, where the governing party, led by Jaroslaw Kaczynski, has taken a similar course against N.G.O.s.

European legal experts have said that the European Union’s efforts to counter the Hungarian law are unlikely to lead to effective sanctions, or change the course of Mr. Orban’s government.

In his speech Thursday, Mr. Soros said, “Democracy cannot be imposed from the outside; it needs to be asserted and defended by the people themselves.”

He acknowledged that in responding to challenges to its core values, the European Union “is cumbersome, slow-moving and often needs unanimity to enforce its rules.”

“This is difficult to achieve when two countries, Poland and Hungary, are conspiring to oppose it,” he said. “It will require resolute action by European institutions and the active engagement of civil society.”

A version of this article appears in print on , on Page A4 of the New York edition with the headline: Soros Sees ‘Mafia State’ Under Hungary’s Leader. Order Reprints | Today’s Paper | Subscribe